Tubular fluorescent lamp



- Feb. 25, 1958 J. A. DE VRIEND ET AL TUBULAR FLUORESCENT LAMP Filed March 9, 1954 R m A EE W G U Mm .H Jw M Y B Fig.

AGENT about .-.3...lr.ntn.s .fl 1 r V In Fig. '4, the space between the tubes 3 and 4 is filled with small glass tubes 9 having an inner diameter of about 2.15 mmsgand an eater diameter of about 4 rams. and each hayinga length ofabout 4 ems, the axes of the tubes-being orientated in parallel with the axis of the discharge lamp 3.. I r a r It-has been found that explosion in the case 'ofJbreakage of 40 watt fluorescenttuhes is avoided'in' the emsurface area,; parallel to the axis of the lamp, larger than V 600cm. #and a section of material equal to at the most {halfthe sectional area of the annular space in which it is provided. "Furthermore, .the' axial flow through apertures arerequired'to be larger than'about 1.8 mm.

.8; Thecspacing between two turns of the band 8 is r a bodiments shown in FigsQZto 4, if the filling mass has a masses possessing a structure having open passages whose,

the envelope causes sufficlent change in the character the gas such that explosion becomes'impossible.

2. A. lamp as'claimed in claim 1 inwhich the filling I 7 mass has a fibrous structure 3. A lamp asclaimed ih'claim 2 the filling mass consists of amember selected from the group'con- V sisting of glasslw ool and metal wool. i a i 10 v V substantially parallelto the'axis oi the lamp.

It will be evident that theimaterial of the filling mass -must;be chosen such thatitcannot detrimentallyafiect the electrodes, the filling (for example '-the mercury),

the fluoreseentsubstances, etc.

What is claimed-is:

l. A tubular fluorescent lamp adapted to operategin a' potentially-explosive, gascontaining environment, com-' "prising an envelope, a low-pressure 'ionizable medium within said envelope, a pair of thermionic electrodes diseach disposed within the envelope completely between one end thereof and the adjacent themionic electrode for p'osed in the envelope eachispaced a' small distance from' I one end ofysaid envelope, and-a .pair of filling masses 5. A lamp as claimed in claim, 4, in which the foil Ina-1 7 7 terial is repeatedly folded with the folding edges parallel to the axis of the lamp.

6. A Ramp as claimed 1; claim l 1 in which the finin mass is constituted by thin tubes having their axes su bstantially'parallel to the axis. of thelamp;

7. A lamp as claimed in claim 3, in' which the space" factor ofthe wool isabout 2%.

8. A lamp as claimed in claim 4 in which the surface. area. of the filling mass,. parallel to the axis ofthe lamp;

is larger'than 600 ;cm.', and the surfacearea of the solid material in a cross-sectiontransverse to the axis is .equal'.

to at the'most half the surface area of the space in which the mass is provided, and axial flow-through apertures in the massare larger than 1.8 mmfl.

References Cited in the file of thispatent UNITED STATES PATENTS h 1,46%187 "Metzger Sept. 4, 1923 1,788,951 Hendry Jan. 13,1931 7 4. A lamp as claimed in claim 1 in which theitillingf consists'of foil material of whichthe surfaee is U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CQRRECTION Patent Noa 2,824,993 February 25, 1958 Johannes Adriaan de Vriend et a1,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let uers Patent should read as corrected below.

' "601mm" 1 line" 20,' for "explosfure' read m explosion line 51, for "abount" read about column 3, line 29, for thermionic" read a thermionic Signed and sealed this 15th day of April 1.958a

Attest:

KARL MINE ROBERT c. WATSON Attesting Officer Comissioner of Patents 

